Systems and methods for reconstructing an audio signal from transformed audio information

ABSTRACT

A system and method may be configured to reconstruct an audio signal from transformed audio information. The audio signal may be resynthesized based on individual harmonics and corresponding pitches determined from the transformed audio information. Noise may be subtracted from the transformed audio information by interpolating across peak points and across trough points of harmonic pitch paths through the transformed audio information, and subtracting values associated with the trough point interpolations from values associated with the peak point interpolations. Noise between harmonics of the sound may be suppressed in the transformed audio information by centering functions at individual harmonics in the transformed audio information, the functions serving to suppress noise between the harmonics.

RELATED APPLICATIONS

This application claims the priority benefit of U.S. provisional patentapplication No. 61/467,493, filed on Mar. 25, 2011, and entitled“Spectral Motion Transformation,” which is hereby incorporated into thisdisclosure by reference in its entirety.

FIELD

The disclosure relates to reconstructing an audio signal obtained from anoisy environment based on pitch and harmonic amplitudes determined fromtransformed audio information and/or suppressing noise between harmonicsof the sound in the transformed audio information by centering functionsat individual harmonics in the transformed audio information.

BACKGROUND

Systems and method for reconstructing an audio signal are known.Existing techniques operate with relative accuracy and precision in thebest of conditions. However, in “noisy” conditions (e.g., either soundnoise or processing noise) the accuracy, precision, and/or speed ofconventional techniques may drop off significantly. Since many of thesettings and/or audio signals in and on which these techniques areapplied may be considered noisy, conventional processing to reconstructan audio signal may be only marginally useful.

SUMMARY

One aspect of the disclosure relates to a system and method ofreconstructing an audio signal from transformed audio information. Theaudio signal may be resynthesized based on individual harmonics andcorresponding pitches determined from the transformed audio information.Noise may be subtracted from the transformed audio information byinterpolating across peak points and across trough points of harmonicpitch paths through the transformed audio information, and subtractingthe trough point interpolations from the peak point interpolations.Noise between harmonics of the sound may be suppressed in thetransformed audio information by centering functions at individualharmonics in the transformed audio information, the functions serving tosuppress noise between the harmonics.

In some implementations, a system may be configured for reconstructingan audio signal from transformed audio information. The system maycomprise one or more processors configured to execute computer programmodules. The computer program modules may comprise one or more of anaudio information module, a resynthesis module, a noise subtractionmodule, a fence model module, a reconstruction module, and/or othermodules.

The audio information module may be configured to obtain transformedaudio information representing one or more sounds. The audio signal mayhave a duration. That is, the audio signal may span a discrete period oftime. The transformed audio information may have been transformed indiscrete time sample windows over the audio signal. The time samplewindows may be overlapping or non-overlapping in time. The transformedaudio information may include pitch and/or pitch information associatedwith the audio signal. In some implementations, pitch and/or pitchinformation may be determined as described in one or both of U.S. patentapplication Ser. No. 13/205,483, filed Aug. 8, 2011, and entitled“System And Method For Tracking Sound Pitch Across An Audio Signal”,and/or U.S. patent application Ser. No. 13/205,521, filed Aug. 8, 2011,and entitled “System And Method For Tracking Sound Pitch Across An AudioSignal Using Harmonic Envelope,” which are hereby incorporated byreference into the present application in their entireties. Thetransformed audio information may specify magnitude of a coefficientrelated to signal intensity as a function of frequency for an audiosignal and time. In some implementations, the transformed audioinformation for the time sample window may include a plurality of setsof transformed audio information. The individual sets of transformedaudio information may correspond to different fractional chirp rates.Obtaining the transformed audio information may include transforming theaudio signal, receiving the transformed audio information in acommunications transmission, accessing stored transformed audioinformation, and/or other techniques for obtaining information.

The resynthesis module may be configured to resynthesize the audiosignal based on individual harmonics and corresponding pitchesdetermined from the transformed audio information. According to someimplementations, resynthesizing the audio signal may include trackingone or more pitches of the sound to determine individual pitches andcorresponding amplitudes as a function of time for individual harmonicsof the sound. Individual harmonics may be synthesized using oscillatorscorresponding to individual harmonics. Synthesizing individual harmonicsmay include, for a given harmonic, integrating a corresponding pitchover time to determine a phase of the given harmonic. Individual ones ofthe oscillators may be based on a cosine function. The synthesizedharmonics may be summed to obtain the resynthesized audio signal.

In some implementations, resynthesis module may be configured to solveany phase problems because the audio signal may be built throughintegration, where phase is a consequence of the audio signal and notsomething that needs to be factored in. Also, the degree of compressionof the resynthesized audio signal may go below a kB per second forvoice.

The resynthesized audio signal may be built from oscillators andparameters that specify pitch and harmonic amplitudes as a function oftime. One or more of these parameters may be adjusted independently ofthe others without altering the phase and without harmonics suddenlydropping out. In some implementations, one or more parameters may beadjusted for pitch shifting, where the same timbre is preserved bypreserving the pattern of harmonic amplitudes. Whisper synthesis may beperformed, according to some implementations, where a set of evenlyspaced harmonics is replaced by a white-noise source. This may preservevowel shapes to give an indication as to what a given person would soundlike if he were whispering.

The noise subtraction module may be configured to subtract noise fromthe transformed audio information. Subtracting noise may includeinterpolating across peak points and trough points of harmonic pitchpaths through the transformed audio information. The peak points may liealong harmonic frequencies in the transformed audio information, and maybe determined as a function of frequency and time for a given harmonic.The trough points may be positioned midway between peak points ofadjacent harmonic frequencies in the transformed audio information, andmay be determined as a function of frequency and/or time. Valuesassociated with individual ones of the trough point interpolations maybe subtracted from values associated with individual ones of the peakpoint interpolations to yield noise-reduced transformed audioinformation.

The fence model module may be configured to suppress noise betweenharmonics of the sound in the transformed audio information by centeringfunctions at individual harmonics in the transformed audio information.The functions may serve to suppress noise between the harmonics in orderto yield noise-reduced transformed audio information. The width of agiven function may be based on a bandwidth of a corresponding harmonic.In some implementations, individual ones of the functions utilized byfence the model module may include a Gaussian function. According tosome implementations, individual ones of the functions may include arectangular function.

The reconstruction module may be configured to reconstruct an audiosignal. In some implementations, one or more reverse transformations maybe performed on transformed audio information and/or othernon-time-domain information to obtain a reconstructed audio signal. Thereconstruction module may be configured to reconstruct noise-reducedtransformed audio information obtained from the noise subtractionmodule, the fence model module, and/or another source of noise-reducedtransformed audio information. A reverse transformation used by thereconstruction module may correspond to a reverse and/or inverse of atransform performed on the original audio signal to produce thetransformed audio information

These and other objects, features, and characteristics of the systemand/or method disclosed herein, as well as the methods of operation andfunctions of the related elements of structure and the combination ofparts and economies of manufacture, will become more apparent uponconsideration of the following description and the appended claims withreference to the accompanying drawings, all of which form a part of thisspecification, wherein like reference numerals designate correspondingparts in the various figures. It is to be expressly understood, however,that the drawings are for the purpose of illustration and descriptiononly and are not intended as a definition of the limits of theinvention. As used in the specification and in the claims, the singularform of “a”, “an”, and “the” include plural referents unless the contextclearly dictates otherwise.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a system configured for reconstructing an audiosignal from transformed audio information, in accordance with one ormore implementations.

FIG. 2 illustrates an exemplary plot of transformed audio information.

FIG. 3 illustrates a method for reconstructing an audio signal fromtransformed audio information by resynthesizing the audio signal basedon individual harmonics and corresponding pitches determined from thetransformed audio information, in accordance with one or moreimplementations.

FIG. 4 illustrates a method for reconstructing an audio signal fromtransformed audio information where noise is subtracted from thetransformed audio information, in accordance with one or moreimplementations.

FIG. 5 illustrates a method for reconstructing an audio signal fromtransformed audio information where noise is suppressed betweenharmonics of the sound in the transformed audio information, inaccordance with one or more implementations.

DETAILED DESCRIPTION

FIG. 1 illustrates a system 10 configured for reconstructing an audiosignal from transformed audio information, in accordance with one ormore implementations. The transformed audio signal may be obtained fromthe audio signal through Fourier Transform, Fast Fourier Transform,Short Time Fourier Transform, Spectral Motion Transform, and/or othertransforms. The audio signal may be resynthesized based on individualharmonics and corresponding pitches determined from the transformedaudio information. Noise may be subtracted from the transformed audioinformation by interpolating across peak points and across trough pointsof harmonic pitch paths through the transformed audio information, andsubtracting the trough point interpolations from the peak pointinterpolations. Noise between harmonics of the sound may be suppressedin the transformed audio information by centering functions atindividual harmonics in the transformed audio information, the functionsserving to suppress noise between the harmonics.

The system 10 may be implemented in an overarching system (not shown)configured to process the audio signal. For example, the overarchingsystem may be configured to segment sounds represented in the audiosignal (e.g., divide sounds into groups corresponding to differentsources, such as human speakers, within the audio signal), classifysounds represented in the audio signal (e.g., attribute sounds tospecific sources, such as specific human speakers), reconstruct soundsrepresented in the audio signal, and/or process the audio signal inother ways. In some implementations, system 10 may include one or moreof one or more processors 12, electronic storage 14, a user interface16, and/or other components.

The processor 12 may be configured to execute one or more computerprogram modules. The computer program modules may be configured toexecute the computer program module(s) by software; hardware; firmware;some combination of software, hardware, and/or firmware; and/or othermechanisms for configuring processing capabilities on processor 12. Insome implementations, the one or more computer program modules mayinclude one or more of an audio information module 18, a resynthesismodule 20, a noise subtraction module 22, a fence model module 24, areconstruction module 26, and/or other modules.

The audio information module 18 may be configured to obtain transformedaudio information representing one or more sounds. The transformed audioinformation may include a transformation of an audio signal into thefrequency domain, a pseudo-frequency domain, a dynamical-frequencydomain, and/or other non-temporal domains. By way of non-limitingexample, the transformed audio information may be transformed from theaudio signal by way of a Fourier transform, a fast-Fourier transform, ashort-time-Fourier transform, and/or other transforms. The transformedaudio information may include pitch and/or pitch information associatedwith the audio signal. In some implementations, pitch and/or pitchinformation may be determined as described one or both of U.S. patentapplication Ser. No. 13/205,483, filed Aug. 8, 2011, and entitled“System And Method For Tracking Sound Pitch Across An Audio Signal”,and/or U.S. patent application Ser. No. 13/205,521, filed Aug. 8, 2011,and entitled “System And Method For Tracking Sound Pitch Across An AudioSignal Using Harmonic Envelope,” which are hereby incorporated byreference into the present application in their entireties. Thetransformed audio information may include a transformation of an audiosignal into a frequency-chirp domain, such as that described in U.S.patent application Ser. No. 13/205,424, filed Aug. 8, 2011, and entitled“System And Method For Processing Sound Signals Implementing A SpectralMotion Transform” which is hereby incorporated into this disclosure byreference in its entirety. The transformed audio information may havebeen transformed in discrete time sample windows over the audio signal.The time sample windows may be overlapping or non-overlapping in time.Generally, the transformed audio information may specify magnitude of acoefficient related to signal intensity as a function of frequency,time, chirp, and/or other parameters for an audio signal within a timesample window.

By way of illustration, FIG. 2 depicts an exemplary plot 28 oftransformed audio information. The plot 28 may depict a magnitude of acoefficient related to energy as a function of frequency. Thetransformed audio information represented by plot 28 may include aharmonic sound, represented by a series of spikes 30 in the magnitude ofthe coefficient at the frequencies of the harmonics of the harmonicsound. Assuming that the sound is harmonic, spikes 30 may be spacedapart at intervals that correspond to the pitch (φ) of the harmonicsound. As such, individual spikes 30 may correspond to individual onesof the overtones of the harmonic sound.

Other spikes (e.g., spikes 32 and/or 34) may be present in thetransformed audio information. These spikes may not be associated withharmonic sound corresponding to spikes 30. The difference between spikes30 and spike(s) 32 and/or 34 may not be amplitude, but insteadfrequency, as spike(s) 32 and/or 34 may not be at a harmonic frequencyof the harmonic sound. As such, these spikes 32 and/or 34, and the restof the amplitude between spikes 30 may be a manifestation of noise inthe audio signal. As used in this instance, “noise” may not refer to asingle auditory noise, but instead to sound (whether or not such soundis harmonic, diffuse, white, or of some other type) other than theharmonic sound associated with spikes 30.

The transformation that yields the transformed audio information fromthe audio signal may result in the coefficient related to signalintensity being a complex number. The transformation may include anoperation to make the complex number a real number. This may include,for example, taking the square of the modulus of the complex number,and/or other operations for making the complex number a real number. Insome implementations, the complex number for the coefficient generatedby the transform may be preserved. In such implementations, for example,the real and imaginary portions of the coefficient may be analyzedseparately, at least at first. By way of illustration, plot 28 mayrepresent the real portion of the coefficient, and a separate plot (notshown) may represent the imaginary portion of the coefficient as afunction of frequency. The plot representing the imaginary portion ofthe coefficient as a function of frequency may have spikes at theharmonics of the harmonic sound that corresponds to spikes 30.

In some implementations, the transformed audio information may representall of the energy present in the audio signal, or a portion of theenergy present in the audio signal. For example, if the transformationof the audio signal places the audio signal into the frequency-chirpdomain, the coefficient related to signal intensity may be specified asa function of frequency and fractional chirp rate. In such examples, thetransformed audio information may include a representation of the energypresent in the audio signal having a common fractional chirp rate (e.g.,a one dimensional slice through a two-dimensional frequency-chirp domainto produce a frequency domain representation with a fixed chirp rateand/or other fixed parameter).

Referring back to FIG. 1, resynthesis module 20 may be configured toresynthesize the audio signal based on individual harmonics andcorresponding pitches determined from the transformed audio information.According to some implementations, resynthesizing the audio signal mayinclude tracking one or more pitches of the sound to determineindividual pitches and corresponding amplitudes as a function of timefor individual harmonics of the sound. Individual harmonics may besynthesized using oscillators corresponding to individual harmonics.Synthesizing individual harmonics may include, for a given harmonic,integrating a corresponding pitch over time to determine the unwrappedphase of the given harmonic. Individual ones of the oscillators may bebased on a cosine function. The synthesized harmonics may be summed toobtain the resynthesized audio signal.

According to some implementations, the output y as a function of time tof the i^(th) oscillator may be expressed as, or similar to,yi(t)=cos∫₀ ^(t) iφ(τ)dτ,where φ is pitch (first harmonic) as a function of time. This equationmay be fixed, so the entire representation of a sound is stored in thepitch and harmonic amplitude parameters. Time courses may be representedsparsely because pitch and envelope (the set of harmonic amplitudes)change slowly per time relative to the sampling rate. For example, acubic spline with 20 knots may provide an accurate fit to the pitch timecourse over one second for a human voice. Similarly, the harmonicamplitudes may be represented with about 10 knots along the frequencydimension and 20 per second in time to form an “amplitude surface”(e.g., amplitude as a function of frequency and time, and/or transformedaudio information) expressing the changing envelope. Some or allharmonic amplitudes and envelopes for synthesizing consonants with awhite noise source may be shaped by such an amplitude surface.

In some implementations, resynthesis module 20 may be configured tosolve any phase problems because the audio signal may be built throughintegration, where phase is a consequence of the audio signal and notsomething that needs to be factored in. Also, the degree of compressionof the resynthesized audio signal may go below a kB per second forvoice, which is far better than the current mp3 standard.

The resynthesized audio signal may be built from oscillators andparameters that specify pitch and harmonic amplitudes as a function oftime. One or more of these parameters may be adjusted independently ofthe others without altering the phase and without harmonics suddenlydropping out.

In some implementations, individual ones of the oscillators may includea white noise source to simulate a whispered version of the voice thatretains word shaping and speech rhythms. Parameters may be altered toadjust for known channel distortions. For example, cell phones varysubtly in their pass-band, but generally have the same approximate highand low roll-offs. A correction may be made by dividing the transformedaudio information by the roll-off transfer function.

The noise subtraction module 22 may be configured to subtract noise fromthe transformed audio information. Subtracting noise may includeinterpolating across peak points of harmonic pitch paths through thetransformed audio information. The peak points may lie along harmonicfrequencies in the transformed audio information, and may be determinedas a function of frequency and time for a given harmonic. In someimplementations, interpolation across the peak points may includepolynomial interpolation, use of splines, and/or other interpolationtechniques.

Subtracting noise may further include interpolating across trough pointsof harmonic pitch paths through the transformed audio information. Thetrough points may be positioned midway between peak points of adjacentharmonic frequencies in the transformed audio information, and may bedetermined as a function of frequency and time. In some implementations,interpolation across the trough points may include polynomialinterpolation, use of splines, and/or other interpolation techniques.Such splines may include linear, quadratic, cubic, and/or other splines.Values associated with individual ones of the trough pointinterpolations may be subtracted from values associated with individualones of the peak point interpolations to yield noise-reduced transformedaudio information.

The fence model module 24 may be configured to suppress noise betweenharmonics of the sound in the transformed audio information by centeringfunctions at individual harmonics in the transformed audio information.The functions may serve to suppress noise between the harmonics in orderto yield noise-reduced transformed audio information. The width of agiven function may be based on a bandwidth of a corresponding harmonic.

In some implementations, individual ones of the functions utilized byfence model module 24 may include a Gaussian function. Such a Gaussianfunction may be configured to suppress information between theharmonics. The Gaussian function may be configured to replaceinformation associated with individual harmonics with Gaussian (orother) curves to provide noise-reduced transformed audio information. Agiven Gaussian curve may be fitted to a corresponding harmonic.

An audio signal may be reconstructed from the noise-reduced transformedaudio information, as discussed in connection with the reconstructionmodule 26. Such a reconstructed audio signal may closely resemble theundistorted original audio signal, even down to 3 dB noise.Additionally, the reconstructed audio signal may be more compactrelative to the original audio signal because only the harmonicfrequencies and corresponding amplitudes need to be transmitted toresynthesize the reconstructed audio signal.

According to some implementations, individual ones of the functions mayinclude a rectangular fence. Such a fence may be configured to zeroinformation between the harmonics while preserving informationassociated with the harmonics. In some implementations, one or morefunctions utilized by fence model module 24 may be separately applied toreal and imaginary components of the transformed audio information.

The reconstruction module 26 may be configured to reconstruct an audiosignal and/or portions of an audio signal (e.g., vowel and/or consonantsounds). In some implementations, one or more reverse transformationsmay be performed on transformed audio information and/or othernon-time-domain information to obtain a reconstructed audio signal. Thatis, reconstruction may include converting a frequency domainrepresentation and/or frequency-chirp domain representation to atime-domain representation, according to some implementations. Thereconstruction module 26 may be configured to reconstruct noise-reducedtransformed audio information obtained from noise subtraction module 22,fence model module 24, and/or another source of noise-reducedtransformed audio information. A reverse transformation used byreconstruction module 26 may correspond to a reverse and/or inverse of atransform performed on the original audio signal to produce thetransformed audio information.

Processor 12 may be configured to provide information processingcapabilities in system 10. As such, processor 12 may include one or moreof a digital processor, an analog processor, a digital circuit designedto process information, an analog circuit designed to processinformation, a state machine, and/or other mechanisms for electronicallyprocessing information. Although processor 12 is shown in FIG. 1 as asingle entity, this is for illustrative purposes only. In someimplementations, processor 12 may include a plurality of processingunits. These processing units may be physically located within the samedevice, or processor 12 may represent processing functionality of aplurality of devices operating in coordination (e.g., “in the cloud”,and/or other virtualized processing solutions).

It should be appreciated that although modules 18, 20, 22, 24, and 26are illustrated in FIG. 1 as being co-located within a single processingunit, in implementations in which processor 12 includes multipleprocessing units, one or more of modules 18, 20, 22, 24, and/or 26 maybe located remotely from the other modules. The description of thefunctionality provided by the different modules 18, 20, 22, 24, and/or26 described below is for illustrative purposes, and is not intended tobe limiting, as any of modules 18, 20, 22, 24, and/or 26 may providemore or less functionality than is described. For example, one or moreof modules 18, 20, 22, 24, and/or 26 may be eliminated, and some or allof its functionality may be provided by other ones of modules 18, 20,22, 24, and/or 26. As another example, processor 12 may be configured toexecute one or more additional modules that may perform some or all ofthe functionality attributed below to one of modules 18, 20, 22, 24,and/or 26.

Electronic storage 14 may comprise electronic storage media that storesinformation. The electronic storage media of electronic storage 14 mayinclude one or both of system storage that is provided integrally (i.e.,substantially non-removable) with system 10 and/or removable storagethat is removably connectable to system 10 via, for example, a port(e.g., a USB port, a firewire port, etc.) or a drive (e.g., a diskdrive, etc.). Electronic storage 14 may include one or more of opticallyreadable storage media (e.g., optical disks, etc.), magneticallyreadable storage media (e.g., magnetic tape, magnetic hard drive, floppydrive, etc.), electrical charge-based storage media (e.g., EEPROM, RAM,etc.), solid-state storage media (e.g., flash drive, etc.), and/or otherelectronically readable storage media. Electronic storage 14 may includevirtual storage resources, such as storage resources provided via acloud and/or a virtual private network. Electronic storage 14 may storesoftware algorithms, information determined by processor 12, informationreceived via user interface 16, and/or other information that enablessystem 10 to function properly. Electronic storage 14 may be a separatecomponent within system 10, or electronic storage 14 may be providedintegrally with one or more other components of system 10 (e.g.,processor 12).

User interface 16 may be configured to provide an interface betweensystem 10 and users. This may enable data, results, and/or instructionsand any other communicable items, collectively referred to as“information,” to be communicated between the users and system 10.Examples of interface devices suitable for inclusion in user interface16 include a keypad, buttons, switches, a keyboard, knobs, levers, adisplay screen, a touch screen, speakers, a microphone, an indicatorlight, an audible alarm, and a printer. It is to be understood thatother communication techniques, either hard-wired or wireless, are alsocontemplated by the present invention as user interface 16. For example,the present invention contemplates that user interface 16 may beintegrated with a removable storage interface provided by electronicstorage 14. In this example, information may be loaded into system 10from removable storage (e.g., a smart card, a flash drive, a removabledisk, etc.) that enables the user(s) to customize the implementation ofsystem 10. Other exemplary input devices and techniques adapted for usewith system 10 as user interface 14 include, but are not limited to, anRS-232 port, RF link, an IR link, modem (telephone, cable or other). Inshort, any technique for communicating information with system 10 iscontemplated by the present invention as user interface 14.

FIG. 3 illustrates a method 36 for reconstructing an audio signal fromtransformed audio information by resynthesizing the audio signal basedon individual harmonics and corresponding pitches determined from thetransformed audio information, in accordance with one or moreimplementations. The operations of method 36 presented below areintended to be illustrative. In some implementations, method 36 may beaccomplished with one or more additional operations not described,and/or without one or more of the operations discussed. Additionally,the order in which the operations of method 36 are illustrated in FIG. 3and described below is not intended to be limiting.

At operation 38, transformed audio information representing a sound maybe obtained. The transformed audio information may specify magnitude ofa coefficient related to signal intensity as a function of frequency forthe audio signal and time. In some implementations, operation 38 may beperformed by an audio information module that is the same as or similarto audio information module 18 (shown in FIG. 1 and described above).

At operation 40, one or more pitches of the sound may be tracked todetermine individual pitches and corresponding amplitudes as a functionof time for individual harmonics of the sound. In some implementations,operation 40 may be performed by a resynthesis module that is the sameas or similar to resynthesis module 20 (shown in FIG. 1 and describedabove).

At operation 42, individual harmonics may be synthesized usingoscillators corresponding to individual harmonics. According to someimplementations, only harmonics associated with a desired sound (e.g.,speech from a particular speaker) within the original audio signal maybe synthesized, thus excluding unwanted sounds. In some implementations,operation 42 may be performed by a resynthesis module that is the sameas or similar to resynthesis module 20 (shown in FIG. 1 and describedabove).

At operation 44, the synthesized harmonics may be summed to obtain theresynthesized audio signal. In some implementations, operation 44 may beperformed by a resynthesis module that is the same as or similar toresynthesis module 20 (shown in FIG. 1 and described above).

FIG. 4 illustrates a method 46 for reconstructing an audio signal fromtransformed audio information where noise is subtracted from thetransformed audio information, in accordance with one or moreimplementations. The operations of method 46 presented below areintended to be illustrative. In some implementations, method 46 may beaccomplished with one or more additional operations not described,and/or without one or more of the operations discussed. Additionally,the order in which the operations of method 46 are illustrated in FIG. 4and described below is not intended to be limiting.

At operation 48, transformed audio information representing a sound maybe obtained. The transformed audio information may specify magnitude ofa coefficient related to signal intensity as a function of frequency forthe audio signal and time. In some implementations, operation 48 may beperformed by an audio information module that is the same as or similarto audio information module 18 (shown in FIG. 1 and described above).

At operation 50, peak points of harmonic pitch paths may be interpolatedthrough the transformed audio information. The peak points may lie alongharmonic frequencies in the transformed audio information, and may bedetermined as a function of frequency and time for a given harmonic. Insome implementations, operation 50 may be performed by a noisesubtraction module that is the same as or similar to noise subtractionmodule 22 (shown in FIG. 1 and described above).

At operation 52, trough points of harmonic pitch paths may beinterpolated through the transformed audio information. The troughpoints may be positioned midway between peak points of adjacent harmonicfrequencies in the transformed audio information, and may be determinedas a function of frequency and time. In some implementations, operation52 may be performed by a noise subtraction module that is the same as orsimilar to noise subtraction module 22 (shown in FIG. 1 and describedabove).

At operation 54, values associated with individual ones of the troughpoint interpolations may be subtracted from values associated withindividual ones of the peak point interpolations to yield noise-reducedtransformed audio information. In some implementations, operation 54 maybe performed by a noise subtraction module that is the same as orsimilar to noise subtraction module 22 (shown in FIG. 1 and describedabove).

At operation 56, the audio signal may be reconstructed based on areverse transformation of the noise-reduced transformed audioinformation. In some implementations, operation 56 may be performed by areconstruction module that is the same as or similar to reconstructionmodule 26 (shown in FIG. 1 and described above).

FIG. 5 illustrates a method 58 for reconstructing an audio signal fromtransformed audio information where noise is suppressed betweenharmonics of the sound in the transformed audio information, inaccordance with one or more implementations. The operations of method 58presented below are intended to be illustrative. In someimplementations, method 58 may be accomplished with one or moreadditional operations not described, and/or without one or more of theoperations discussed. Additionally, the order in which the operations ofmethod 58 are illustrated in FIG. 5 and described below is not intendedto be limiting.

At operation 60, transformed audio information representing a sound maybe obtained. The transformed audio information may specify magnitude ofa coefficient related to signal energy as a function of frequency forthe audio signal and time. In some implementations, operation 60 may beperformed by an audio information module that is the same as or similarto audio information module 18 (shown in FIG. 1 and described above).

At operation 62, noise between harmonics of the sound may be suppressedin the transformed audio information by centering functions atindividual harmonics in the transformed audio information. The functionsmay serve to suppress noise between the harmonics to yield noise-reducedtransformed audio information. The width of a given function may bebased on a bandwidth of a corresponding harmonic. In someimplementations, operation 62 may be performed by a fence model modulethat is the same as or similar to fence model module 24 (shown in FIG. 1and described above).

At operation 64, the audio signal may be reconstructed based on areverse transformation of the noise-reduced transformed audioinformation. In some implementations, operation 64 may be performed by areconstruction module that is the same as or similar to reconstructionmodule 26 (shown in FIG. 1 and described above).

In some implementations, methods 36, 46, and/or 58 may be implemented inone or more processing devices (e.g., a digital processor, an analogprocessor, a digital circuit designed to process information, an analogcircuit designed to process information, a state machine, and/or othermechanisms for electronically processing information). The one or moreprocessing devices may include one or more devices executing some or allof the operations of methods 36, 46, and/or 58 in response toinstructions stored electronically on an electronic storage medium. Theone or more processing devices may include one or more devicesconfigured through hardware, firmware, and/or software to bespecifically designed for execution of one or more of the operations ofmethods 36, 46, and/or 58.

Although the system(s) and/or method(s) of this disclosure have beendescribed in detail for the purpose of illustration based on what iscurrently considered to be the most practical and preferredimplementations, it is to be understood that such detail is solely forthat purpose and that the disclosure is not limited to the disclosedimplementations, but, on the contrary, is intended to covermodifications and equivalent arrangements that are within the spirit andscope of the appended claims. For example, it is to be understood thatthe present disclosure contemplates that, to the extent possible, one ormore features of any implementation can be combined with one or morefeatures of any other implementation.

What is claimed is:
 1. A method for reconstructing an audio signal fromtransformed audio information, the method comprising: obtainingtransformed audio information representing a sound, wherein thetransformed audio information specifies magnitude of a coefficientrelated to signal intensity as a function of frequency for the audiosignal and time; and resynthesizing the audio signal based on individualharmonics and corresponding pitches determined from the transformedaudio information, wherein resynthesizing the audio signal includes:tracking one or more pitches of the sound to determine individualpitches and corresponding amplitudes as a function of time forindividual harmonics of the sound, synthesizing individual harmonicsusing oscillators corresponding to individual harmonics, and summing thesynthesized harmonics to obtain the resynthesized audio signal.
 2. Themethod of claim 1, wherein synthesizing individual harmonics includes,for a given harmonic, integrating a corresponding pitch over time todetermine a phase of the given harmonic.
 3. The method of claim 1,wherein individual ones of the oscillators are based on a cosinefunction.
 4. The method of claim 1, wherein individual ones of theoscillators include a white noise source.